Double tube for heat-exchange

Abstract

Disclosed herein is a double tube for heat exchange. The double tube for heat exchange includes: a spiral pipe having ridges and valleys alternately formed on a circumferential surface thereof along a spiral track thereof and guiding a first fluid to flow therethrough; an outer pipe receiving the spiral pipe axially inserted thereinto and guiding a second fluid to flow along the circumferential surface of the spiral pipe in an axial direction such that the second fluid exchanges heat with the first fluid; and a resistance member protruding from the spiral pipe or the valleys to increase residence time of the second fluid in the valleys on the circumferential surface of the spiral pipe and to support the ridges adjacent thereto. Unlike typical double tubes, the double tube for heat exchange can improve heat exchange efficiency between a second fluid flowing inside an outer pipe and a fluid flowing inside a spiral pipe axially inserted into the outer pipe to increase residence time of the second fluid inside the outer pipe by virtue of a spiral shape of the spiral pipe; can improve flow directionality of the second fluid through formation of the grooves in valleys of the spiral pipe along a spiral track of the valleys; can reduce flow-induced noise through expansion of a space defined between an end joint of the outer pipe and the inner pipe to reduce the pressure of the second fluid; and further improve heat exchange efficiency through resistance members protruding from the valleys to increase residence time of the second fluid.

What is claimed is: 
     
       1. A double tube for heat exchange, the double tube comprising:
 a spiral pipe having ridges and valleys alternately formed on a circumferential surface thereof along a spiral track thereof and guiding a first fluid to flow therethrough; 
 an outer pipe receiving the spiral pipe axially inserted thereinto and guiding a second fluid to flow along the circumferential surface of the spiral pipe in an axial direction such that the second fluid exchanges heat with the first fluid; 
 a first pipe expansion joint coupled to a first end of the spiral pipe and the outer pipe; 
 a second pipe expansion joint coupled to a second end of the spiral pipe and the outer pipe; 
 the first pipe expansion joint having a flattened portion formed by flattening a curved circumferential surface of the first inner pipe expansion joint, the flattened portion configured to facilitate weldability; 
 a first port for the second fluid and the first port is welded on the flattened portion of the first inner pipe expansion joint, the first port configured to receive the second fluid as a high temperature and high pressure fluid; 
 a second port for the second fluid and attached to the second inner pipe expansion joint, the second port configured to discharge the second fluid as heat exchanged second fluid; 
 the flattened portion creates a space expansion portion separately formed in an inner surface of the first pipe expansion joint to mitigate welding defects and reduce flow-induced noise; 
 a plurality of resistance members; and 
 wherein a resistance member of the plurality of resistance members is formed across a plurality of valleys. 
 
     
     
       2. The double tube of  claim 1 , wherein each of the pipe expansion joints has a flattened portion formed by flattening a curved circumferential surface of a pipe expansion portion to create a space expansion portion inside the flattened portion and to improve weldability of the ports. 
     
     
       3. The double tube of  claim 1 , further comprising first and second inner pipes configured to allow the first fluid to flow therethrough. 
     
     
       4. The double tube of  claim 1 , the first and second pipe expansion joints configured to have a greater diameter than the outer pipe. 
     
     
       5. The double tube of  claim 1 , the first and second pipe expansion joints being sealed against the corresponding pipe of the inner pipes and the first and second ports for introducing and discharging the second fluid, respectively. 
     
     
       6. The double tube of  claim 1 , the circumferential surface of the spiral pipe having at least one groove formed along a spiral track thereof to improve flow directionality of the second fluid and to increase a contact area between the second fluid and the spiral pipe. 
     
     
       7. The double tube of  claim 6 , the at least one groove is configured to increase residence time of the second fluid in the outer pipe. 
     
     
       8. The double tube of  claim 7 , the at least one groove comprises four grooves. 
     
     
       9. The double tube of  claim 1 , the first port configured for inflow of the second fluid and the second port configured for outflow of the second fluid. 
     
     
       10. The double tube of  claim 1 , the second fluid coming from a condenser at a relatively high temperature and high pressure and at a higher temperature than the first fluid. 
     
     
       11. The double tube of  claim 1 , the outer tube configured to completely surround the spiral pipe. 
     
     
       12. The double tube of  claim 1 , the second pipe expansion joint having an expansion portion with an expanded space between second pipe expansion and the spiral pipe to reduce transfer pressure and transfer rate of the second fluid through the second port to reduce flow-induced noise. 
     
     
       13. The double tube of  claim 1 , further comprising a plurality of resistance members formed in the valleys of the spiral tube. 
     
     
       14. The double tube of  claim 13 , the plurality of resistance members having a chamfered upper portion. 
     
     
       15. The double tube of  claim 1 , the valleys comprise a plurality of grooves. 
     
     
       16. A double tube for heat exchange, comprising:
 a spiral pipe having ridges and valleys alternately formed on a circumferential surface thereof along a spiral track thereof and guiding a first fluid to flow therethrough; 
 an outer pipe receiving the spiral pipe axially inserted thereinto and guiding a second fluid to flow along the circumferential surface of the spiral pipe in an axial direction such that the second fluid exchanges heat with the first fluid; 
 inner pipes (connected to opposite sides of the spiral pipe to allow the first fluid to flow therethrough; and 
 pipe expansion joints provided at opposite sides of the outer pipe to have a greater diameter than the outer pipe to be placed at junctions of the spiral pipe and the inner pipes, pipe expansion joints being sealed against the corresponding pipe of the inner pipes and provided with ports for introducing and discharging the second fluid, respectively, 
 wherein the pipe expansion joints include pipe expansion portions having a greater diameter than the outer pipe and integrally connected to the outer pipe, 
 wherein each of the valleys has at least three grooves formed along the spiral track, and 
 wherein a resistance member is protruded at least partially over the remaining grooves except for two grooves located outside among the at least three grooves. 
 
     
     
       17. The double tube of  claim 16 , wherein the first fluid is a refrigerant. 
     
     
       18. The double tube of  claim 16 , wherein the first fluid is at a lower pressure than the second fluid. 
     
     
       19. The double tube of  claim 16 , wherein each of the pipe expansion joints has a flattened portion.